As automotive and other industries strive to reduce the weight and enhance the quality of their products, a need has arisen for lightweight materials which can be used in structural components where a high level of confidence in performance is required.
High-pressure die casting (HPDC) is a process used for economically producing large volumes of industrial castings. HPDC offers the attributes of excellent surface finish, nearness to net shape, dimensional accuracy, thin walls, and fine detail. However, HPDC has thus far been unable to match the quality of other casting processes. For example, gravity casting processes are routinely expected to produce high-integrity castings. HPDC has a reputation of being a process which involves a number of limiting casting defects. Such defects include high levels of porosity from entrapped gas and solidification shrinkage, linear defects from incoherent streams of metal flow, and cracking from cooling stresses. To address such concerns, today's practitioner usually designs load-bearing die castings so that they incorporate a large safety factor. Accordingly, HPDC has tended to be relegated to applications involving less stringent load or pressure bearing requirements.
The HPDC industry continues to address the issue of casting defects. Some effort has been focused on developing enhanced HPDC processes which attempt to overcome the perceived quality shortcomings in relation to other casting processes, while retaining inherently high productivity.
The North American Die Casting Association on Oct. 18, 1993 presented a paper entitled "Two-Furnace Melting System For Magnesium," authored by Holta, et al. That paper discussed the problems of melting alloy ingots of light metals such as magnesium and transferring them to a casting machine. The paper discussed the introduction of protective gas mixtures and the utilization of heated steel tubes for melt handling. Also disclosed was a siphon tube to feed a die casting machine.